1. Field of Invention
Various exemplary embodiments relate generally to an electronic device, and more particularly, to a semiconductor memory device and an operating method thereof.
2. Description of Related Art
Semiconductor memory devices are typically categorized into volatile memory devices and non-volatile memory devices.
Volatile memory devices operate at high write and read speeds, but they are unable to retain their stored data when their power supply is interrupted. Non-volatile memory devices operate at relatively low write and read speeds, but they may retain the stored data without a constant source of power. Examples of non-volatile memory devices include Read Only Memory (ROM), Mask ROM (MROM), Programmable ROM (PROM), Erasable Programmable ROM (EPROM), Electrically Erasable Programmable ROM (EEPROM), flash memory, Phase-change Random Access Memory (PRAM), Magnetic RAM (MRAM), Resistive RAM (RRAM) and Ferroelectric RAM (FRAM). Flash memories are categorized into NOR and NAND types.
Flash memories have the advantages of both RAM and ROM. For example, flash memories may be freely programmed and erased similar to RAM, and flash memories may retain their stored data even when their power is interrupted, similar to ROM. Flash memories have been widely used as storage media of portable electronic devices such as mobile phones, digital cameras, personal digital assistants (PDAs), and MP3 players.
A semiconductor memory device may include a plurality of memory blocks including a plurality of memory cells. In the semiconductor memory device, two memory blocks may share one row decoder, i.e., an X-decoder. In semiconductor memory devices having this configuration, when a read operation is performed on a selected memory block between two other memory blocks, electron-hole pairs (EHP) may be generated due to a gate-induced-drain-leakage (GIDL) phenomenon between a bit line and a drain selection transistor and between a source line and a source selection transistor, in cell strings included in an unselected memory block. As a result, the width of the memory cell threshold voltage distribution of the unselected memory block may increase.